It is known to prepare light-sensitive silver halide crystals by a precipitation method using a water-soluble halide and a water-soluble silver salt in the presence of a protective colloid.
Also, it is known as described in, for example, H. Frieser, et al., Die Grundlagen der Photographischen Prozesse mit Silberhalogeniden, pages 631-640 (published by Akademische Verlagsgesellschaft, 1968) that the environmental conditions for forming the precipitates influence the crystal appearance of silver halide grains.
A technique capable of being applied to control the crystal appearance of silver bromide is generally described in PS & E Journal, Vol. 12, pages 207-212 (1968) by F. H. Claes and W. Peelaers. This report describes in detail the transfer of the positive or twin isometric system of silver bromide having the {100} crystal appearance specified by the (100) plane into an octahedron system having the {111} habit and the (111) plane.
Hitherto, for silver bromide emulsions or silver iodobromide emulsions, silver halide grains composed of the (100) crystal plane and/or the (111) crystal plane have been studied and used.
As a silver halide emulsion having the (110) crystal plane, a silver chloride emulsion or a silver chlorobromide emulsion is known. For example, Japanese Patent Publication No. 42737/80 describes a silver chloride emulsion and also a silver chlorobromide emulsion containing 50 mol % or 75 mol % silver bromide. However, there is no description about a silver bromide emulsion or silver iodobromide emulsion having the (110) crystal plane in the patent publication.
Also, West German Patent Application (OLS) No. 2,932,185 describes silver chloride grains having the (110) plane but there is no description about a silver bromide emulsion and silver iodobromide emulsion having the (110) plane in the specification of the patent application.
Also, there is a description about silver bromide grains which are said to simultaneously have the (111) plane, the (100) plane and the (110) plane in Photo. Sci. Eng., 19 (3), 21 (1975) but there is no description of the evidence used to identify that the plane is the (110) plane. The only evidence is from photographs attached to the report. Furthermore, from the photographs of the silver halide grains, it is difficult to determine whether the silver bromide grains are a rhombic dodecahedron or not. Even if the silver bromide grains may contain the (110) plane, it is simply assumed that the occupying ratio of the (110) plane to the whole grain surfaces is very small. Also, there is only the description about the method of preparation of the silver bromide grains but the utilization of the silver bromide grains as a photographic silver halide emulsion is not described in the aforesaid report.
Moreover, in the above-described report, the physical ripening of the silver halide grains is performed in the presence of pyridine but pyridine does not have the function of sufficiently growing the (110) plane. Thus, it can be said that the silver bromide grains disclosed in the above report do not belong to the category of the silver halide grains in the present invention.
Thus, the silver bromide emulsion and the silver iodobromide emulsion each having the (110) plane have not been known before our invention.